Optical fiber has acquired an increasingly important role in the field of telecommunications, frequently replacing existing copper wires. This trend has had a significant impact in all areas of telecommunications, which has seen a vast increase in the usage of fiber. Further increases in the use of optical fiber is at least foreseen in local loop telephone and cable TV service, as local, wide area and other fiber networks are established to deliver ever greater volumes of information in the form of data, audio, and video signals to residential and commercial users. In addition, use of fiber in home and commercial business environments for internal data, voice, and video communications has begun and is expected to increase.
Optical cables are thus now used for many long-distance and local communication links, and in the nature of such links they may pass through areas where they may be accessible to those who might wish to eavesdrop on the transmitted data for the purpose of governmental or “industrial” espionage or to facilitate criminal acts of various kinds. A long optical cable link, if accessible, may not be too difficult to tap without detection; for example, if the signal level is high, a sufficient signal may sometimes be extracted by “microbending” the fiber carrying the data without the reduction in intensity at the receiving end of the fiber becoming obvious; or a more sophisticated eavesdropper might induce a cable breakdown and install a tap (possibly incorporating an optical amplifier to compensate losses) downstream of the fault before it can be repaired by the operator of the installation. Another possibility is that the cable may be tapped during deployment when a fiber link is being installed.
Certain applications require a very high degree of security to ensure that sensitive information cannot be accessed by unauthorized parties. For instance, government agencies, financial institutions and other organizations require assurances that their confidential information transmitted over a communications link will not be compromised. Such security is particularly vulnerable at the time a link is first installed. During installation, there is a possibility that the fiber could be deliberately tapped or hacked for illegal purposes. For instance, a splice could be added to the fiber as it is payed out from the fiber reel. While such illegal acts may be readily detected once a link is installed and operational, there is generally no assurance that security will not be breached during the installation period.
Accordingly, it would be desirable to provide a method and apparatus for ensuring the security of a fiber link as it is being installed.